This invention relates to electromagnetic radiation output level testing, and more particularly to a device, removably attachable to the end of an optical fiber, allowing visual determination of whether light emitted by the fiber exceeds a threshold value.
In many applications it is important to be able to verify that a system designed to deliver optical energy to a substrate is actually operating at the required level of delivered energy. For example, when light is applied to cure (e.g., by polymerization) a light-curable material, it can be important to know that sufficient energy has been delivered to accomplish the intended or required degree of cure. One common example of such a tester is a light meter, as used in photography. Other, representative examples are described in the following documents.
U.S. Pat. No. 5,772,656 describes a light source for use in ophthalmic procedures, including a photoreactive element that reacts with laser radiation in a manner proportional to the intensity or intensity profile of the laser beam and an aligner for disposing the photoreactive element in the path of a laser beam.
U.S. Pat. Nos. 5,441,530 and 5,527,349 describe a photochemotherapy dosimeter for monitoring cumulative photochemotherapy radiation dosage. The dosimeter includes an optical fiber having a chemical cell containing a photobleachable chemical attached at one end. The chemical cell, in use, is positioned near abnormal tissue which is subjected to photochemotherapy treatment.
U.S. Pat. No. 4,863,282 describes a sun heat radiation sensor including a heat activatable liquid crystal composition selected to provide quantitative visual indication of sun heat radiation.
U.S. Pat. Nos. 5,019,074, 5,395,356 and 5,807,379 describe, generally, laser systems for reprofiling a surface, including a laser and an erodible element disposed between the laser and the surface to be reprofiled to provide a predefined profile of resistance to erosion by laser radiation. Upon irradiation of the element, a portion of the laser radiation is selectively absorbed and another portion is transmitted to the surface in accordance with the element profile to selectively erode the surface.
U.S. Pat. No. 5,052,820 describes thermo-optical sensing devices provided at various sections of an optical fiber that exhibit temperature dependent indices of refraction. The sensing devices define temperature sensitive areas that control the transmission of light through the optical fiber thereby allowing detection of temperature changes along the fiber.
U.S. Pat. No. 5,051,597 describes a radiation dosage indicator including visible indicia that exhibits a change depending upon whether the indicator has been irradiated.
While the above and other references describe, in many cases, useful testing devices, many of these systems have drawbacks. For example, in certain applications where a light meter is used, the light meter needs to be calibrated, and is vulnerable to loss of battery power, especially when used irregularly. Moreover, electronic instruments can be difficult to sterilize, for use in a surgical or other medical environment, or in a clean room.
Accordingly, it is an object of the present invention to provide a simplified, improved electromagnetic radiation tester.
The present invention provides an electromagnetic radiation power output testing device (herein, a xe2x80x9cpower testerxe2x80x9d, a xe2x80x9ctesterxe2x80x9d or simply a xe2x80x9cdevicexe2x80x9d) that can provide a response when an appropriate level of energy is provided to the device from a source of electromagnetic radiation, to insure that exposure of a target article or a patient to electromagnetic radiation will accomplish an intended effect.
Because of the cost and difficulty of sterilizing items in a safe and validatable manner, in one embodiment of the invention the tester is designed for sterilization. The tester is preferably disposable, to eliminate the need for recalibration, cleaning and resterilization. This in turn makes it advantageous to have a power tester which is inexpensive to fabricate, yet which can be easily designed and adapted for use in a particular situation. In its simplest embodiment, the tester is a device for determining electromagnetic radiation emission. The device includes a photoresponsive element constructed and arranged to be positioned in a fixed spatial relationship with respect to a source of electromagnetic radiation. In one embodiment, the device is arranged for removable attachment to a selected source of electromagnetic radiation. The element is capable of exhibiting a change in a visible characteristic responsive to electromagnetic radiation from the source to which it is attached. The photoresponsive element is not ablated by the electromagnetic radiation.
In another embodiment the device includes a thermochromic element mounted on a positioner providing a fixed spatial relationship between an optical source and the thermochromic element. A preferred positioner is a body, which carries the thermochromic element and which mates to the output region of the optical system. To use the tester, it is aligned with the output of the optical source to be tested, for example by inserting a light fiber into an opening in a tester; and the optical source is operated for a defined period. A change in color (for example) of the thermochromic element signifies that the optical source is emitting sufficient power for its intended application.
In yet another embodiment the device is designed for determining whether a laser, constructed and arranged for use in a clinical procedure, emits light above a threshold level. The device in this embodiment includes a thermochromic element constructed and arranged for removable attachment to an end of an optical fiber connected to a laser. The thermochromic element exhibits a change in visible characteristic when its temperature exceeds a threshold value, and is positioned on a body removably attachable to an end of the optical fiber. The thermochromic element and body are, together, sterilizable in this embodiment.
In another aspect the invention provides methods for determining emission from a source of electromagnetic radiation. In one embodiment the method involves exposing a photoresponsive element to electromagnetic radiation from a source in proximity with the element, and determining whether interaction of the electromagnetic radiation with the photoresponsive element causes a change in the element. This change is indicative of a specific, predetermined threshold level of electromagnetic radiation acceptable for a specific procedure. The method involves using the source in the procedure if the level of electromagnetic radiation is acceptable. The source is rejected for use in the procedure if the level of electromagnetic radiation is not acceptable.
In another embodiment a method involves providing a tester, the tester comprising a thermochromic element capable of absorbing energy from a source of electromagnetic radiation. The thermochromic element is characterized in exhibiting a change in a visible characteristic when its temperature exceeds a threshold value. The tester also includes a positioner to hold the thermochromic element in a defined spatial relationship with respect to the light source. The detector is positioned at the output location of the source, and the source is operated for a predetermined length of time. Response of the thermochromic element then is observed, and observation of a response or lack of a response of the thermochromic element determines whether the electromagnetic radiation output does or does not exceed a predetermined level.
In methods and devices of the invention a demarcation zone can be provided on the photoresponsive element, the demarcation zone defining a testing zone. In this embodiment the tester can be positioned so that electromagnetic radiation output from a source illuminates essentially all of the testing zone, and observation of a response or lack of response of the testing zone is carried out.
Further useful features provided in systems and methods of the invention, in some embodiments, include optical wavelength filters; means for determining if the optical system is functioning; collimating elements; focusing elements, such as lenses; sterilizability; air draft minimization; thermal buffering; low cost, to provide disposability; and means for determining maximum power output or irradiance as well as minimum.
Other advantages, novel features, and objects of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings, which are schematic and which are not intended to be drawn to scale. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention.